Understanding Command Modes

The command modes available in the traditional Cisco IOS CLI are exactly the same as the command modes available in Cisco IOS XE.

You use the CLI to access Cisco IOS XE software. Because the CLI is divided into many different modes, the commands available to you at any given time depend on the mode that you are currently in. Entering a question mark ( ? ) at the CLI prompt allows you to obtain a list of commands available for each command mode.

When you log in to the CLI, you are in user EXEC mode. User EXEC mode contains only a limited subset of commands. To have access to all commands, you must enter privileged EXEC mode, normally by using a password. From privileged EXEC mode, you can issue any EXEC command—user or privileged mode—or you can enter global configuration mode. Most EXEC commands are one-time commands. For example, show commands show important status information, and clear commands clear counters or interfaces. The EXEC commands are not saved when the software reboots.

Configuration modes allow you to make changes to the running configuration. If you later save the running configuration to the startup configuration, these changed commands are stored when the software is rebooted. To enter specific configuration modes, you must start at global configuration mode. From global configuration mode, you can enter interface configuration mode and a variety of other modes, such as protocol-specific modes.

ROM monitor mode is a separate mode used when the Cisco IOS XE software cannot load properly. If a valid software image is not found when the software boots or if the configuration file is corrupted at startup, the software might enter ROM monitor mode.

Table 1-1 describes how to access and exit various common command modes of the Cisco IOS XE software. It also shows examples of the prompts displayed for each mode.

To return to privileged EXEC mode from global configuration mode, use the exit or end command.

Interface configuration

From global configuration mode, specify an interface using an interface command.

Router(config-if)#

To return to global configuration mode, use the exit command.

To return to privileged EXEC mode, use the end command.

Diagnostic

The router boots up or accesses diagnostic mode in the following scenarios:

In some cases, diagnostic mode will be reached when the IOS process or processes fail. In most scenarios, however, the router will reload.

A user-configured access policy was configured using the transport-map command that directed the user into diagnostic mode. See the “ Console Port, Telnet, and SSH Handling” chapter of this book for information on configuring access policies.

The router was accessed using a Route Switch Processor auxiliary port.

A break signal ( Ctrl-C , Ctrl-Shift-6 , or the send break command ) was entered and the router was configured to go into diagnostic mode when the break signal was received.

Router(diag)#

If the IOS process failing is the reason for entering diagnostic mode, the IOS problem must be resolved and the router rebooted to get out of diagnostic mode.

If the router is in diagnostic mode because of a transport-map configuration, access the router through another port or using a method that is configured to connect to the Cisco IOS CLI.

If the router is accessed through the Route Switch Processor auxiliary port, access the router through another port. Accessing the router through the auxiliary port is not useful for customer purposes anyway.

ROM monitor

From privileged EXEC mode, use the reload EXEC command. Press the Break key during the first 60 seconds while the system is booting.

>

To exit ROM monitor mode, use the continue command.

Understanding Diagnostic Mode

Diagnostic mode is supported on the Cisco ASR 903 Series Router.

The router boots up or accesses diagnostic mode in the following scenarios:

The IOS process or processes fail, in some scenarios. In other scenarios, the RSP will simply reset when the IOS process or processes fail.

A user-configured access policy was configured using the transport-map command that directs the user into diagnostic mode.

The router was accessed using a Route Switch Processor auxiliary port.

A send break signal ( Ctrl-C or Ctrl-Shift-6 ) was entered while accessing the router, and the router was configured to enter diagnostic mode when a break signal was sent.

In diagnostic mode, a subset of the commands that are also available in User EXEC mode are made available to users. Among other things, these commands can be used to:

Inspect various states on the router, including the IOS state.

Replace or roll back the configuration.

Provide methods of restarting the IOS or other processes.

Reboot hardware, such as the entire router, an RSP, an IM, or possibly other hardware components.

Transfer files into or off of the router using remote access methods such as FTP, TFTP, SCP, and so on.

The diagnostic mode provides a more comprehensive user interface for troubleshooting than previous routers, which relied on limited access methods during failures, such as ROMmon, to diagnose and troubleshoot IOS problems.

The diagnostic mode commands are stored in the non-IOS packages on the Cisco ASR 903 Series Router, which is why the commands are available even if the IOS process is not working properly. Importantly, all the commands available in diagnostic mode are also available in privileged EXEC mode on the router even during normal router operation. The commands are entered like any other commands in the privileged EXEC command prompts when used in privileged EXEC mode.

Accessing the CLI Using a Router Console

The following sections describe how to access the command-line interface (CLI) using a directly-connected console or by using Telnet or a modem to obtain a remote console:

Accessing the CLI Using a Directly-Connected Console

This section describes how to connect to the console port on the router and use the console interface to access the CLI. The console port is located on the front panel of each Route Switch Processor (RSP).

Connecting to the Console Port

Before you can use the console interface on the router using a terminal or PC, you must perform the following steps:

Step 3 From user EXEC mode, enter the enable command as shown in the following example:

Router> enable

Step 4 At the password prompt, enter your system password. If an enable password has not been set on your system, this step may be skipped. The following example shows entry of the password called “enablepass”:

Step 6 You now have access to the CLI in privileged EXEC mode and you can enter the necessary commands to complete your desired tasks.

Step 7 To exit the console session, enter the quit command as shown in the following example:

Router# quit

Accessing the CLI from a Remote Console Using Telnet

This section describes how to connect to the console interface on a router using Telnet to access the CLI.

Preparing to Connect to the Router Console Using Telnet

Before you can access the router remotely using Telnet from a TCP/IP network, you need to configure the router to support virtual terminal lines (vtys) using the line vty global configuration command. You also should configure the vtys to require login and specify a password.

Note To prevent disabling login on the line, be careful that you specify a password with the password command when you configure the login line configuration command. If you are using authentication, authorization, and accounting (AAA), you should configure the login authentication line configuration command. To prevent disabling login on the line for AAA authentication when you configure a list with the login authentication command, you must also configure that list using the aaa authentication login global configuration command. For more information about AAA services, refer to the Cisco IOS XE Security Configuration Guide, Release 2and Cisco IOS Security Command Reference publications.

In addition, before you can make a Telnet connection to the router, you must have a valid host name for the router or have an IP address configured on the router. For more information about requirements for connecting to the router using Telnet, information about customizing your Telnet services, and using Telnet key sequences, refer to the Cisco IOS Configuration Fundamentals Configuration Guide, Release 12.2SR .

Using Telnet to Access a Console Interface

To access a console interface using Telnet, complete the following steps:

Step 1 From your terminal or PC, enter one of the following commands:

connect host [ port ] [ keyword ]

telnet host [ port ] [ keyword ]

In this syntax, host is the router hostname or an IP address, port is a decimal port number (23 is the default), and keyword is a supported keyword. For more information, refer to the Cisco IOS Configuration Fundamentals Command Reference .

Note If you are using an access server, then you will need to specify a valid port number such as telnet 172.20.52.40 2004, in addition to the hostname or IP address.

The following example shows the telnet command to connect to the router named “router”:

unix_host% telnet router

Trying 172.20.52.40...

Connected to 172.20.52.40.

Escape character is '^]'.

unix_host% connect

Step 2 At the password prompt, enter your login password. The following example shows entry of the password called “mypass”:

User Access Verification

Password: mypass

Note If no password has been configured, press Return.

Step 3 From user EXEC mode, enter the enable command as shown in the following example:

Router> enable

Step 4 At the password prompt, enter your system password. The following example shows entry of the password called “enablepass”:

Step 6 You now have access to the CLI in privileged EXEC mode and you can enter the necessary commands to complete your desired tasks.

Step 7 To exit the Telnet session, use the exit or logout command as shown in the following example:

Router# logout

Accessing the CLI from a Remote Console Using a Modem

To access the router remotely using a modem through an asynchronous connection, connect the modem to the console port.

The console port on a Cisco ASR 903 Series Router is an EIA/TIA-232 asynchronous, serial connection with no flow control and an RJ-45 connector. The console port is located on the front panel of the RSP.

To connect a modem to the console port, place the console port mode switch in the in position. Connect to the port using the RJ-45-to-RJ-45 cable and the RJ-45-to-DB-25 DCE adapter (labeled “Modem”).

To connect to the router using the USB console port, connect to the port using a USB Type A-to-Type A cable.

Recall commands in the history buffer, beginning with the most recent command. Repeat the key sequence to recall successively older commands.

Ctrl-N or the Down Arrow key1

Return to more recent commands in the history buffer after recalling commands with Ctrl-P or the Up Arrow key.

Router# show history

While in EXEC mode, list the last several commands you have just entered.

2.The arrow keys function only on ANSI-compatible terminals such as VT100s.

Getting Help

Entering a question mark ( ? ) at the CLI prompt displays a list of commands available for each command mode. You can also get a list of keywords and arguments associated with any command by using the context-sensitive help feature.

To get help specific to a command mode, a command, a keyword, or an argument, use one of the following commands:

Table 1-4 Help Commands and Purpose

Command

Purpose

help

Provides a brief description of the help system in any command mode.

abbreviated-command-entry ?

Provides a list of commands that begin with a particular character string. (No space between command and question mark.)

abbreviated-command-entry <
Tab >

Completes a partial command name.

?

Lists all commands available for a particular command mode.

command ?

Lists the keywords or arguments that you must enter next on the command line. (Space between command and question mark.)

Finding Command Options Example

This section provides an example of how to display syntax for a command. The syntax can consist of optional or required keywords and arguments. To display keywords and arguments for a command, enter a question mark ( ? ) at the configuration prompt or after entering part of a command followed by a space. The Cisco IOS XE software displays a list and brief description of available keywords and arguments. For example, if you were in global configuration mode and wanted to see all the keywords or arguments for the arap command, you would type arap ? .

The <cr> symbol in command help output stands for “carriage return.” On older keyboards, the carriage return key is the Return key. On most modern keyboards, the carriage return key is the Enter key. The <cr> symbol at the end of command help output indicates that you have the option to press Enter to complete the command and that the arguments and keywords in the list preceding the <cr> symbol are optional. The <cr> symbol by itself indicates that no more arguments or keywords are available and that you must press Enter to complete the command.

Table 1-5 shows examples of how you can use the question mark ( ? ) to assist you in entering commands.

Table 1-5 Finding Command Options

Command

Comment

Router>
enable

Password:
<password>

Router#

Enter the enable command and password to access privileged EXEC commands. You are in privileged EXEC mode when the prompt changes to a “ # ” from the “ > ”; for example, Router> to Router# .

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#

Enter the configure terminal privileged EXEC command to enter global configuration mode. You are in global configuration mode when the prompt changes to Router(config)# .

Router(config)#
interface serial ?

<0-6> Serial interface number

Router(config)#
interface serial 4 ?

/

Router(config)#
interface serial 4/ ?

<0-3> Serial interface number

Router(config)#
interface serial 4/0 ?

<cr>

Router(config)#
interface serial 4/0

Router(config-if)#

Enter interface configuration mode by specifying the serial interface that you want to configure using the interface serial global configuration command.

Enter ? to display what you must enter next on the command line. In this example, you must enter the serial interface slot number and port number, separated by a forward slash.

When the <cr> symbol is displayed, you can press Enter to complete the command.

You are in interface configuration mode when the prompt changes to Router(config-if)# .

Router(config-if)#
?

Interface configuration commands:

.

.

.

ip Interface Internet Protocol config commands

keepalive Enable keepalive

lan-name LAN Name command

llc2 LLC2 Interface Subcommands

load-interval Specify interval for load calculation for an

interface

locaddr-priority Assign a priority group

logging Configure logging for interface

loopback Configure internal loopback on an interface

mac-address Manually set interface MAC address

mls mls router sub/interface commands

mpoa MPOA interface configuration commands

mtu Set the interface Maximum Transmission Unit (MTU)

netbios Use a defined NETBIOS access list or enable

name-caching

no Negate a command or set its defaults

nrzi-encoding Enable use of NRZI encoding

ntp Configure NTP

.

.

.

Router(config-if)#

Enter ? to display a list of all the interface configuration commands available for the serial interface. This example shows only some of the available interface configuration commands.

Router(config-if)#
ip ?

Interface IP configuration subcommands:

access-group Specify access control for packets

accounting Enable IP accounting on this interface

address Set the IP address of an interface

authentication authentication subcommands

bandwidth-percent Set EIGRP bandwidth limit

broadcast-address Set the broadcast address of an interface

cgmp Enable/disable CGMP

directed-broadcast Enable forwarding of directed broadcasts

dvmrp DVMRP interface commands

hello-interval Configures IP-EIGRP hello interval

helper-address Specify a destination address for UDP broadcasts

hold-time Configures IP-EIGRP hold time

.

.

.

Router(config-if)#
ip

Enter the command that you want to configure for the interface. This example uses the ip command.

Enter ? to display what you must enter next on the command line. This example shows only some of the available interface IP configuration commands.

Router(config-if)#
ip address ?

A.B.C.D IP address

negotiated IP Address negotiated over PPP

Router(config-if)#
ip address

Enter the command that you want to configure for the interface. This example uses the ip address command.

Enter ? to display what you must enter next on the command line. In this example, you must enter an IP address or the negotiated keyword.

A carriage return (<cr>) is not displayed; therefore, you must enter additional keywords or arguments to complete the command.

Router(config-if)#
ip address 172.16.0.1 ?

A.B.C.D IP subnet mask

Router(config-if)#
ip address 172.16.0.1

Enter the keyword or argument that you want to use. This example uses the 172.16.0.1 IP address.

Enter ? to display what you must enter next on the command line. In this example, you must enter an IP subnet mask.

A <cr> is not displayed; therefore, you must enter additional keywords or arguments to complete the command.

Enter ? to display what you must enter next on the command line. In this example, you can enter the secondary keyword, or you can press Enter .

A <cr> is displayed; you can press Enter to complete the command, or you can enter another keyword.

Router(config-if)#
ip address 172.16.0.1 255.255.255.0

Router(config-if)#

In this example, Enter is pressed to complete the command.

Using the no and default Forms of Commands

Almost every configuration command has a no form. In general, use the no form to disable a function. Use the command without the no keyword to re-enable a disabled function or to enable a function that is disabled by default. For example, IP routing is enabled by default. To disable IP routing, use the no ip routing command; to re-enable IP routing, use the ip routing command. The Cisco IOS software command reference publications provide the complete syntax for the configuration commands and describe what the no form of a command does.

Many CLI commands also have a default form. By issuing the command default command-name , you can configure the command to its default setting. The Cisco IOS software command reference publications describe the function of the default form of the command when the default form performs a different function than the plain and no forms of the command. To see what default commands are available on your system, enter default ? in the appropriate command mode.

Saving Configuration Changes

Use the copy running-config startup-config command to save your configuration changes to the startup configuration so that the changes will not be lost if the software reloads or a power outage occurs. For example:

Router# copy running-config startup-config

Building configuration...

It might take a minute or two to save the configuration. After the configuration has been saved, the following output appears:

[OK]

Router#

This task saves the configuration to NVRAM.

Managing Configuration Files

On the Cisco ASR 903 Series Router, the startup configuration file is stored in the nvram: file system and the running-configuration files are stored in the system: file system. This configuration file storage setup is not unique to the Cisco ASR 903 Series Router and is used on several Cisco router platforms.

As a matter of routine maintenance on any Cisco router, users should backup the startup configuration file by copying the startup configuration file from NVRAM onto one of the router’s other file systems and, additionally, onto a network server. Backing up the startup configuration file provides an easy method of recovering the startup configuration file in the event the startup configuration file in NVRAM becomes unusable for any reason.

The copy command can be used to backup startup configuration files. Below are some examples showing the startup configuration file in NVRAM being backed up:

Filtering Output from the show and more Commands

You can search and filter the output of show and more commands. This functionality is useful if you need to sort through large amounts of output or if you want to exclude output that you need not see.

To use this functionality, enter a show or more command followed by the “pipe” character ( | ); one of the keywords begin , include , or exclude ; and a regular expression on which you want to search or filter (the expression is case sensitive):

The output matches certain lines of information in the configuration file. The following example illustrates how to use output modifiers with the show interface command when you want the output to include only lines in which the expression “protocol” appears:

Router# show interface | include protocol

FastEthernet0/0 is up, line protocol is up

Serial4/0 is up, line protocol is up

Serial4/1 is up, line protocol is up

Serial4/2 is administratively down, line protocol is down

Serial4/3 is administratively down, line protocol is down

Powering Off the Router

Before you turn off a power supply, make certain the chassis is grounded and you perform a soft shutdown on the power supply. Not performing a soft shutdown will often not harm the router, but may cause problems in certain scenarios.

To perform a soft shutdown before powering off the router, enter the reload command to halt the system and then wait for ROM Monitor to execute before proceeding to the next step.

Place the power supply switch in the Off position after seeing this message.

Finding Support Information for Platforms and Cisco Software Images

Cisco software is packaged in feature sets consisting of software images that support specific platforms. The feature sets available for a specific platform depend on which Cisco software images are included in a release. To identify the set of software images available in a specific release or to find out if a feature is available in a given Cisco IOS XE software image, you can use Cisco Feature Navigator or the software release notes.

Using Cisco Feature Navigator

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn . An account on Cisco.com is not required.

Using Software Advisor

To see if a feature is supported by a Cisco IOS XE release, to locate the software document for that feature, or to check the minimum software requirements of Cisco IOS XE software with the hardware installed on your router, Cisco maintains the Software Advisor tool on Cisco.com at http://www.cisco.com/cgi-bin/Support/CompNav/Index.pl.

You must be a registered user on Cisco.com to access this tool.

Using Software Release Notes

Cisco IOS XE software releases include release notes that provide the following information:

Platform support information

Memory recommendations

New feature information

Open and resolved severity 1 and 2 caveats for all platforms

Release notes are intended to be release-specific for the most current release, and the information provided in these documents may not be cumulative in providing information about features that first appeared in previous releases. Refer to Cisco Feature Navigator for cumulative feature information.